Investigating the characteristic strength of flocs formed from crude and purified Hibiscus extracts in water treatment

The growth, breakage and re-growth of flocs formed using crude and purified seed extracts of Okra (OK), Sabdariffa (SB) and Kenaf (KE) as coagulants and coagulant aids was assessed. The results showed floc size increased from 300μm when aluminium sulphate (AS) was used as a coagulant to between 696μm and 722μm with the addition of 50mg/l of OK, KE and SB crude samples as coagulant aids. Similarly, an increase in floc size was observed when each of the purified proteins was used as coagulant aid at doses of between 0.123 and 0.74mg/l. The largest floc sizes of 741μm, 460μm and 571μm were obtained with a 0.123mg/l dose of purified Okra protein (POP), purified Sabdariffa (PSP) and purified Kenaf (PKP) respectively. Further coagulant aid addition from 0.123 to 0.74mg/l resulted in a decrease in floc size and strength in POP and PSP. However, an increase in floc strength and reduced d50 size was observed in PKP at a dose of 0.74mg/l. Flocs produced when using purified and crude extract samples as coagulant aids exhibited high recovery factors and strength. However, flocs exhibited greater recovery post-breakage when the extracts were used as a primary coagulant. It was observed that the combination of purified proteins and AS improved floc size, strength and recovery factors. Therefore, the applications of Hibiscus seeds in either crude or purified form increases floc growth, strength, recoverability and can also reduce the cost associated with the import of AS in developing countries.